Is Ovaltine supposed to taste a little sour/odd?!
In my experience, yes, Ovaltine does have a slightly more sour flavour, I think this is due to the extra malt in it. But just to be sure, try it with some other milk.
There is a regular chocolate Ovaltine and a chocolate MALT Ovaltine. Is the container orange or blue? Personally, I love the malt one. But i can see how it would taste a little sour.